This multidisciplinary project examines heterosexual partnerships and networks among patients seeking STD) evaluation. Thus far 1239 respondents have provided detailed data on over 2500 unique sexual partnerships. These data will be compared with a pending separately funded Seattle general population survey which will employ the same questionnaire instrument. We plan to apply selected items from the current questionnaire more widely in routine standardized interviews of all Seattle patients reported with gonococcal and chlamydia infection and syphilis; to expand analyses of partnership/network characteristics associated with these 3 infections; and also to use qualitative methods to describe sexual partnership formation, maintenance and dissolution. Because we find partnership discordances for sexual activity class, race/ethnicity, and age to be associated with STD risk, we will use in- depth semi-structured interviews, applying theories of choice (exchange) and scripting to study social and psychological factors associated with discordance/concordance for these three variables. We plan further to apply insights gained from these quantitative and qualitative approaches to design and conduct two randomized trials of partner notification for preventing reinfection with N. gonorrhoeae or C. trachomatis. The first trial will involve randomizing patients treated in the private sector to achieve partner referral or no active referral. The second will take advantage of technologic advances (urine for diagnosis of chlamydia infection and possibly gonorrhea; single dose, safe, oral therapy for both infections) to randomize patients treated in public sector categorical STD/Family-Planing Clinics to standard partner referral, versus expedited patient management in the field via index patient or disease intervention specialist. Evaluation will involve use of rescreening and registries to document reinfection. Mathematical modeling will be used to assess the potential impact of these interventions at the population level, and to use our empirical data to model the epidemiology of gonorrhea, chlamydia infection and syphilis for this project, and HPV infection for Project by Koutsky.